A known grille shutter device disclosed in JP58-139519U (which will be hereinafter referred to as Reference 1) may control a flow rate of air flowing from a grille opening portion into an engine compartment, in accordance with opening and closing operations of a shutter mechanism provided at the grille opening portion arranged at a front portion of a vehicle body.
In other words, according to the grille shutter device disclosed in Reference 1, the shutter mechanism is brought in a closed state, for example, while a vehicle is moving at high speed; thereby, the flow rate of the air taken into the engine compartment is restricted. Therefore, aerodynamic performance of the vehicle may be increased (for example, a “Cd value” that is a value for coefficient of drag may be decreased). Meanwhile, according to the grille shutter device of Reference 1, a flow rate of air taken into a radiator is restricted when an engine is started; thereby, a period of time to warm up the engine may be reduced. In addition, according to the grille shutter device of Reference 1, for example, in a case where a temperature of the engine tends to rise, the shutter mechanism is brought in an opened state to thereby increase the flow rate of the air flowing into the engine compartment. Therefore, the temperature of the engine may be appropriately controlled.
In general, various heat exchangers (for example, a condenser for an air conditioner) are provided in an engine compartment. Air flowing from a grille opening portion to the engine compartment comes into contact with the heat exchangers and thereby the heat exchangers may appropriately and stably operate in the same way as the aforementioned radiator.
However, a flow rate of the air required by each of the heat exchangers is not consistently uniform and the timing when the flow rate of the air changes is not uniform. For example, in a so-called hybrid vehicle driven by driving forces of an engine and a motor, a temperature of an electric power system (for example, an inverter) of the hybrid vehicle tends to suddenly change. Therefore, a flow rate of air brought into contact with a radiator for a hybrid system of the hybrid vehicle may become insufficient. In such case, the known grille shutter device disclosed in Reference 1 may not allow the plural heat exchangers in the hybrid vehicle to stably operate.
A need thus exists for a grille shutter device which is not susceptible to the drawbacks